Sterically emcumbered bidentate and tridentate naphthoxy-imine metallic complexes

ABSTRACT

The present invention discloses post-metallocene complexes based on sterically encumbered bi- and tri-dentate naphthoxy-imine ligands. It also relates to the use of such post-metallocene complexes in the oligomerization of ethylene to selectively prepare vinyl-end capped linear alpha-olefins.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of PCT/EP2009/054947, filed Apr. 24,2009, which claims priority from EP 08290410.3, filed Apr. 28, 2008.

The present invention relates to the field of post-metallocene complexesbased on sterically encumbered bi- and tri-dentate naphthoxy-imineligands. It also relates to the use of such post-metallocene complexesin the oligomerisation of ethylene to selectively prepare vinyl-endcapped linear alpha-olefins.

There is a need for new highly active alkene polymerisation catalystsystems based on post-metallocenes and a lot of research has beencarried out in that field, such as reviewed for example in Gibson andSptizmesser (Gibson, V. C.; Spitzmesser, S. K. in Chem. Rev. 2003, 103,283) or in Ittel et al. (Ittel, S. D.; Johnson, L. K.; Brookhart, M. inChem. Rev. 2000, 100, 1169 or in Britovsek et al. (Britovsek, G. J. P.;Gibson, V. C.; Wass, D. F. in Angew. Chem., Int. Ed. 1999, 38, 429).

Among the plethora of newly disclosed catalytic systems, discrete group3-6 metal complexes bearing various chelating aryloxide-based ligandshave demonstrated astonishing performances in the polymerisation ofethylene and α-olefins. In particular, industry-relevant highlyeffective Cr(III) based phenoxy-imine systems were scrutinized by Gibsonet al., such as disclosed for example in Jones et al. (Jones, D. J.;Gibson, V. C.; Green, S. M.; Maddox, P. J.; White, A. J. P.; Williams,D. J. in J. Am. Chem. Soc. 2005, 127, 11037) or in Meurs et al. (vanMeurs, M.; Britovsek, G. J. P.; Gibson, V. C.; Cohen, S. A. in J. Am.Chem. Soc. 2005, 127, 9913) or in Gibson and O'Reilly (Gibson, V. C.;O'Reilly, R. K. US 20060258867A1) or in Gibson et al. (Gibson, V. C.;Mastroianni, S.; Newton, C.; Redshaw, C.; Solan, G. A.; White, A. J. P.;Williams, D. J. Dalton Trans. 2000, 1969). Typical metallic complexes ofthis family are represented in FIG. 1.

LIST OF FIGURES

FIG. 1 represents various Cr(III) phenoxy-imino compounds disclosed inliterature that are suitable for the oligomerisation or polymerisationof ethylene.

FIG. 2 represents the scheme used for the preparation of {ONN}H and{ON}H pro-ligands.

FIG. 3 represents the ¹H NMR spectrum of pro-ligand 2a.

FIG. 4 represents the molecular structure of pro-ligand 2a.

FIG. 5 represents the ¹H NMR spectrum of pro-ligand 2b.

FIG. 6 represents the ¹H NMR spectrum of pro-ligand 2c.

FIG. 7 represents the molecular structure of chromium complex 3a.

FIG. 8 represents the molecular structure of chromium complex 3b.

FIG. 9 represents a typical ¹H NMR spectrum of vinyl end-cappedoligoethylenes produced with the system 3a/MAO.

FIG. 10 represents a typical ¹³C NMR (high field region) spectrum ofvinyl end-capped oligoethylenes produced with the system 3a/MAO.

There is however still a need to develop new, very active catalystsystems having specific functionalities in order to tailor polymers withdesired properties.

It is an aim of the present invention to prepare sterically encumberedligands based on naphthoxy groups.

It is also an aim of the present invention to prepare very activecatalyst systems for the oligomerisation and polymerisation of ethyleneand alpha-olefins.

Any one of these aims is, at least partially, fulfilled by the presentinvention.

Accordingly, the present invention discloses a pro-ligand of formula Ior its tautomeric form of formula I′

Wherein R¹, R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected fromhydrogen, unsubstituted or substituted hydrocarbyl, or inert functionalgroup, wherein two or more of said groups can be linked together to formone or more rings,

wherein Z is an atom selected from group 14 of the Periodic Table,

wherein each R² is independently selected from a substituted orunsubstituted aryl group having at most 8 carbon atoms, and/or an alkylgroup, with the restriction that Z(R²)₃ is a bulky group, at least asbulky as tertio-butyl,

wherein R⁸ is a unsubstituted or substituted, aliphatic or aromatichydrocarbyl group, possibly containing donor atoms such as halogens, oratoms selected from groups 15 and 16 of the periodic Table such as N, P,O, S.

Alternatively, Z(R²)₃ can be a substituted aryl group.

Preferably R¹, R³, R⁴, R⁵, R⁶ and R⁷ are each independently selectedfrom hydrogen or alkyl groups having at most 6 carbon atoms, morepreferably they all are hydrogen.

Preferably R⁸ is CH₂-(2-pyridyl), alpha-quinoleine or C₆F₅.

Preferably, Z is C or Si, more preferably, it is Si.

Preferably all R² are the same and are substituted or unsubstitutedphenyl group, or higher aromatic group (e.g. naphtyl), or alkyl. Morepreferably, each R² is unsubstituted phenyl group or a tertio-butylgroup.

By inert functional group, is meant a group, other than hydrocarbyl orsubstituted hydrocarbyl, that is inert under the complexation conditionsto which the compound containing said group is subjected. They can beselected for example from halo, ester, ether, amino, imino, nitro,cyano, carboxyl, phosphate, phosphonite, phosphine, phosphinite,thioether and amide. Preferably, they are selected from halo, such aschloro, bromo, fluoro and iodo, or ether of formula—OR* wherein R* isunsubstituted or substituted hydrocarbyl. After metallation of theligand, an inert functional group must not coordinate to the metalcentre.

The present ligand includes a naphtoxy group whereas most ligandsdisclosed in the prior art include a phenoxy group. The catalyst systemsbased on the present ligand that includes a naphtoxy group are moretolerant thanks to a combination of steric and/or electronic effects.

In addition, in the preferred ligands according to the presentinvention, Z is Si. Replacing C by Si also results in improving thetolerance of the catalyst system. For example, a catalyst system whereinZ is C sees its activity destroyed by the addition of acetonitrile,whereas there is no observed change either in activity or inoligomer/polymer properties for an equivalent catalyst system wherein Zis Si.

Several procedures have been tested in order to prepare the ligands ofthe present invention, most of them without success.

They can be prepared in good yield starting from 2-methoxynapthalene bya process that comprises the steps of:

-   -   a) providing 2-methoxynaphthalene of formula

-   -   b) reacting with (R²)₃ZX′, wherein X′ is an halogen, in the        presence of sec-BuLi in a solvent to obtain a compound of        formula

-   -   c) reacting with N-bromosuccinimide to obtained a compound of        formula

-   -   d) reacting with DMF in the presence of 2 equivalents of        tert-BuLi in a solvent to obtain a compound of formula

-   -   e) deprotecting the compound obtained in step d) in order to        obtain a compound of formula

-   -   f) condensation of the compound obtained in step e) with amine        R⁸—NH₂ in the presence of catalytic amounts of about 1 mol-% of        formic acid, to obtain a compound of formula I and its        tautomeric form I′.

The method of preparation can be summarised in the scheme presented inFIG. 2. Deprotection step e) can be carried out for example by treatmentwith BBr₃.

The acid of step f) can be selected for example from HCOOH or PTSA.

The invention also discloses metallic complexes of general formula II

Metallic complexes II result from the complexation of pro-ligand I (I′)with metallic salts MX_(n) in a solvent, wherein M is a metal Group 6 ofthe periodic Table, wherein each X is the same or different and is analkyl, benzyl substituted or not, aryl substituted or not, amido,alkoxide, and/or halide such as Cl, Br or I, and wherein L² is a solventsuch as for example acetonitrile, THF or pyridine, preferablyacetonitrile.

Preferably X are either all the same and are Br, or one X is para-tolyland the other X is Br.

Preferably M is chromium.

Preferably one equivalent of metallic salt is used per naphthoxy-iminecomplex.

The metallation reaction is carried out at a temperature of from −80° C.to a temperature of +25° C. and for a period of time of 1 to 18 hours.

The present invention also discloses a catalyst system comprising theGroup 6 metal single-site catalyst component of formula II and anactivating agent having an alkylating/ionising action.

Suitable activating agents are well known in the art. The activatingagent can be an aluminium alkyl represented by formula AIR⁺ _(n)X_(3-n)wherein R⁺ is an alkyl having from 1 to 20 carbon atoms and X is ahalogen, in combination with [Ph₃C][B(C₆F₅)₄]. The preferred aluminiumalkyls are triisobutylaluminium (TIBAL) or triethylaluminium (TEAL).Aluminium alkyls are used in combination with trityl.

Alternatively, it can be aluminoxane and comprise oligomeric linearand/or cyclic alkyl aluminoxanes represented by formula

for oligomeric, linear aluminoxanes and by formula

for oligomeric, cyclic aluminoxane,wherein n is 1-40, preferably 1-20, m is 3-40, preferably 3-20 and R* isa C₁-C₈ alkyl group and preferably methyl or isobutyl.

Preferably, the activating agent is methylaluminoxane (MAO).

The amount of activating agent is selected to give an AI/M ratio of from500 to 10000, preferably of from to 1000 to 5000. The amount ofactivating agent depends upon its nature.

Suitable boron-containing agents may also be used for activating Group 6metal single-site catalyst component of formula II where R^($) is analkyl or benzyl group. These include for example a triphenylcarbeniumboronate such as tetrakis(pentafluorophenyl)borato-triphenylcarbenium asdescribed in EP-A-0427696, or those of the general formula [L′-H]⁺ [BAr₁ Ar₂ X₃X₄]⁻ as described in EP-A-0277004 (page 6, line 30 to page 7,line 7).

The amount of boron-containing activating agent is selected to give aB/M ratio of from 0.5 to 5, preferably of about 1.

In another embodiment, according to the present invention, thesingle-site catalyst component of formula II may be deposited on aconventional support. Preferably, the conventional support is silicaimpregnated with MAO. Alternatively the support may also be anactivating support such as fluorinated alumina silica.

The catalyst system may comprise an optional scavenger that may beselected from triethylaluminium, triisobutylaluminum,tris-n-octylaluminium, tetraisobutyldialuminoxane or diethylzinc.

The present invention discloses a method for the oligomerisation or thehomo- or co-polymerisation of ethylene and alpha-olefins that comprisesthe steps of:

-   -   a) injecting the active catalyst system into the reactor;    -   b) injecting the monomer and optional comonomer either before or        after or simultaneously with step a);    -   c) maintaining under polymerisation conditions;    -   d) retrieving the oligomers and/or polymer.

The pressure in the reactor can vary from 0.5 to 50 bars, preferablyfrom 5 to 25 bars.

The polymerisation temperature can range from 10 to 100° C., preferablyfrom 25 to 85° C.

The preferred monomer and optional comonomer can be selected fromethylene, propylene, 1-hexene. The preferred monomer is ethylene.

EXAMPLES

All experiments were performed under a purified argon atmosphere usingstandard Schlenk techniques, or in a glovebox. Solvents were distilledunder nitrogen, from Na/benzophenone for THF and Et₂O, from CaH₂ foracetonitrile and from Na/K alloy for toluene and pentane. They weredegassed thoroughly and stored under nitrogen prior to use. Deuteratedsolvents (benzene-d₆, toluene-d₈, THE-d₈; >99.5% D, Eurisotop) werevacuum-transferred from Na/K alloy into storage tubes. Startingmaterials were purchased from Acros, Strem and Aldrich. NMR spectra ofcomplexes were recorded on Bruker AC-200, AC-300 and AM-500spectrometers in Teflon-valved NMR tubes at 25° C. unless otherwiseindicated. ¹H and ¹³C chemical shifts are reported in ppm vs. SiMe₄ andwere determined by reference to the residual solvent peaks. Assignmentof resonances for organometallic complexes was made from ¹H—¹³C HMQC andHMBC NMR experiments. Coupling constants are given in Hertz. Elementalanalyses were performed by the Microanalytical Laboratory at theInstitute of Chemistry of Rennes and are the average of two independentdeterminations.

I. Preparation of {ONN}H and {ON}H Ligands A. Preparation of3-methoxy-2naphthyl-triphenylsilane

A solution of 15.3 mL of sec-BuLi 1.3 M in hexane/cyclohexane (19.91mmol) was added dropwise to a stirred solution of 3.0 g of2-methoxynaphthalene (18.96 mmol) in 70 mL of tetrahydrofuran (THF) at atemperature of −30° C. and for a period of time of 15 min. Afterstirring overnight at room temperature, to the resultant tinted solutionwas added a solution of 5.87 g of Ph₃SiCl (19.91 mmol) and 3.46 mL ofhexamethylphosphoramide (HMPA) (19.88 mmol) in 50 mL of THF. Thereaction mixture was heated at reflux for a period of time of 20 h,cooled and diluted with 500 mL of water. The organic part was extractedwith 3 times 50 mL of Et₂O. The combined organic extracts were driedover MgSO₄, and evaporated. The crude residue was recrystallised fromheptane and dried under vacuum to give 7.11 g of(3-methoxy-2-naphthyl)(triphenyl)silane (17.07 mmol) with a yield of90%.

The NMR spectrum was as follows:

¹H NMR (200 MHz, CDCl₃, 25° C.): δ 7.80 (m, 2H), 7.67 (m, 7H), 7.55-7.23(m, 12H), 3.69 (s, 3H, OCH₃).

Anal. calcd. for C₂₉H₂₄OSi: C, 83.61; H, 5.81. Found: C, 82.15; H, 5.23.

B. Preparation of (4-bromo-3-methoxy-2-naphtyl)-triphenylsilane

A 150 mL Schlenk flask was charged with 4.68 g of(3-methoxy-2-naphthyl)(triphenyl)silane (11.23 mmol) and 2.20 g ofN-bromosuccinimide (NBS) (12.36 mmol) under argon followed by additionof 10 mL of dimethylformamide (DMF). The resultant mixture was stirredovernight at room temperature, then diluted with 500 mL of water andextracted with 3 times 50 mL of CH₂Cl₂. The combined organic extractswere washed with 200 mL of water, brine and dried over Na₂SO₄. Theproduct was purified by passing through short column (silica) using amixture heptane:EtOAc in a ratio of 15:1 as eluent to afford 5.28 g ofproduct as off-white solid (10.66 mmol) with a yield of 96%.

The NMR spectrum was as follows:

¹H NMR (200 MHz, CDCl₃, 25° C.): δ 8.29 (d, J=8.4 Hz, 1H), 7.80 (s, 1H),7.66 (m, 8H), 7.52-7.27 (m, 10H), 3.18 (s, 3H, OCH₃).

Anal. calcd. for C₂₉H₂₃BrOSi: C, 70.30; H, 4.68. Found: C, 68.99; H,4.56.

C. Preparation of 2-hydroxy-3-(triphenylsilyl)-1-naphthaldehyde (1)

A solution of 16.1 mL of tert-BuLi 1.5 M in pentane (24.10 mmol) wasadded dropwise to a stirred solution of 6.02 g of(4-bromo-3-methoxy-2naphtyl)-triphenylsilane (12.05 mmol) in 50 mL ofEt₂O at −78° C. The reaction mixture was stirred during 1.5 h at a giventemperature and 30 min at 0° C. followed by addition of 0.94 mL of DMF.The resultant mixture was stirred overnight at room temperature anddiluted with 200 mL of water. The organic part was extracted with CH₂Cl₂(3×50 mL). The combined organic extracts were dried over MgSO₄. Theresultant solution was transferred to a Schlenk flask under argon and asolution of 24.1 mL of BBr₃ 1M in CH₂Cl₂ (24.1 mmol) was added dropwiseat −78° C. The reaction mixture was stirred overnight at roomtemperature, then carefully hydrolysed with 500 mL of water. The organicpart was extracted with CH₂Cl₂ (3×50 mL). The combined organic extractswere dried over MgSO₄, and evaporated. The crude residue wasrecrystallised from methanol and dried under vacuum to give 5.44 g of 1(12.63 mmol) with a yield of 95%.

The NMR spectrum was as follows:

¹H NMR (200 MHz, CDCl₃, 25° C.): δ 13.58 (s, 1H, OH), 10.88 (s, 1H,═CHO), 8.40 (d, J=8.4 Hz, 1H), 8.03 (s, 1H), 7.67 (m, 6H), 7.43 (m,12H).

Anal. calcd. for C₂₉H₂₂O₂Si: C, 80.90; H, 5.15. Found: C, 80.17; H,4.67.

D. Preparation of1-[(quinolin-8-ylamino)methylene]-3-(triphenylsilyl)naphthalen-2-one(2a) as a stable tautomeric form of1-[(quinolin-8-ylimino)methyl]-3-(triphenylsilyl)-2-naphthol

To a stirred mixture of 1.09 g (2.53 mmol) of 1 and 0.37 g (2.53 mmol)of 8-aminoquinoline in 40 mL of methanol, was added formic acid (ca. 10mg) at room temperature. The resultant mixture was stirred at reflux for25 hours and the product precipitated as microcrystalline powder. Thereaction mixture was transferred onto a Schott filter and filtered. Theobtained orange solid was washed with cold methanol and dried undervacuum to give 0.77 g (1.38 mmol) of 2a with a yield of 55%.

The NMR spectra were as follows:

¹H NMR (500 MHz, CD₂Cl₂, 25° C.): δ 15.31 (d, J=11.1 Hz, 1H, NH), 9.31(d, J=11.1 Hz, 1H, ═CHN), 9.02 (dd, 1H), 8.26 (dd, 1H), 8.07 (d, J=8.2Hz, 1H), 7.81 (m, 2H), 7.73 (m, 7H), 7.66 (m, 1H), 7.57-7.40 (m, 12H),7.27 (m, 1H).

¹³C NMR (125 MHz, CD₂Cl₂, 25° C.): δ 185.2, 151.7, 150.1, 146.4, 139.8,137.4, 136.4, 136.1, 135.8, 135.0, 133.2, 130.0, 129.3, 129.2, 129.0,127.7, 126.6, 126.5, 124.4, 123.5, 122.3, 118.3, 113.9, 108.2.

The ¹H NMR of the pro-ligand is represented in FIG. 3.

Anal. calcd. for C₃₈H₂₈N₂OSi: C, 81.98; H, 5.07. Found: C, 81.04; H,4.98.

The molecular structure of this ligand can be seen in FIG. 4.

E. Preparation of1-{[(pyridin-2-ylmethyl)amino]methylene}-3-(triphenylsilyl)naphthalen-2-one(2b) as a stable tautomeric form of1-[(pyridin-2-ylmethyl)imino]methyl)-3-(triphenylsilyl)-2-naphthol

Using the same protocol as described above, pro-ligand 2b was preparedin 0.78 g yield (1.50 mmol, 60%) from 1.08 g of 1 (2.51 mmol) and 0.29 gof 2-aminomethylpyridine (1.50 mmol).

The NMR spectra were as follows:

¹H NMR (500 MHz, CD₂Cl₂, 25° C.): δ 14.44 (br m, 1H, NH), 8.96 (d, J=8.8Hz, 1H), 8.63 (dd, 1H), 7.95 (d, J=8.8 Hz, 1H), 7.79 (s, 1H), 7.70 (m,1H), 7.67 (m, 6H), 7.60-7.35 (m, 11H), 7.32 (d, 1H), 7.25 (m, 1H), 7.23(m, 1H), 4.88 (m, 2H, CH₂Py).

¹³C NMR (125 MHz, CD₂Cl₂, 25° C.): δ 180.6, 158.6, 156.4, 149.8, 149.3,136.9, 136.3, 135.6, 135.1, 131.5, 129.8, 129.2, 128.9, 127.7, 126.1,122.8, 122.6, 121.9, 117.8, 106.1, 57.7.

The ¹H NMR of the pro-ligand is represented in FIG. 5.

Anal. calcd. for C₃₅H₂₈N₂OSi: C, 80.73; H, 5.42. Found: C, 79.94; H,5.00.

F. Preparation of1-[(pentafluorophenyl)imino]methyl}-3-(triphenylsilyl)-2-naphthol (2c)

Pro-ligand 2c was synthesised by condensation of 1.04 g of 1 (2.42 mmol)and 0.44 g of pentafluoro-aniline (2.42 mmol) in toluene at reflux for40 hours in the presence of PTSA (ca. 5% w), using Dean-Stark apparatus.The reaction mixture was evaporated and the residue was recrystallizedfrom methanol to give 2c in 0.93 g yield (1.57 mmol, 65%).

The NMR spectra were as follows:

¹H NMR (500 MHz, CDCl₃, 25° C.): δ 14.49 (s, 1H, OH), 9.76 (s, 1H), 8.13(d, J=8.5 Hz, 1H), 7.96 (s, 1H), 7.71 (d, J=6.7 Hz, 6H), 7.69 (d, J=10.2Hz, 1H), 7.62 (t, J=10.2 Hz, 1H), 7.52-7.30 (m, 10H).

¹³C NMR (125 MHz, CDCl₃, 25° C.): δ 168.5, 165.9, 148.1, 136.4, 134.2,134.0, 130.2, 129.6, 129.4, 127.9, 127.7, 126.3, 123.9, 118.9, 108.8(signals from the Ph group were hardly observed).

¹⁹F NMR (188 MHz, CDCl₃, 25° C.): δ-152.4 (m, 2F), −159.1 (t, 1F),−162.8 (m, 2F).

The ¹H NMR of the pro-ligand is represented in FIG. 6.

Anal. calcd. for C₃₅H₂₂F₅NOSi: C, 70.58; H, 3.72. Found: C, 69.89; H,3.14.

II. Preparation of complexes A. Synthesis of Complex (p-Tol)CrBr₂(THF)₃

Synthesis of Complex (p-Tol)CrBr₂(THF)₃ was performed using modifiedprocedure published in (Daly, J. J.; Sneeden, R. P. A.; Zeiss, H. H. J.Am. Chem. Soc. 1966, 88, 4287-4288) from CrCl₃ and (p-Tol)MgBr in THF.

Anal. calcd. for C₁₉H₃₁Br₂CrO₃: C, 43.95; H, 6.02. Found: C, 43.81; H,5.78.

B. Synthesis of Complex (ONN^(Quin))CrBr₂(MeCN) (3a)

A Schlenk tube was charged with 0.150 g of 2a (0.269 mmol) and 0.140 gof (p-Tol)CrBr₂(THF)₃ (0.269 mmol), and 5 mL of toluene were vacuumtransferred therein. The reaction mixture was stirred overnight at roomtemperature, evaporated and dried in vacuum. The deep-pink residue wasrecrystallised from 20-25 mL of dried acetonitrile to give 0.187 g(0.232 mmol) of 3a with a yield of 86%.

UV-vis (CH₂Cl₂, 298 K, mol^(−l)·dm³·cm⁻¹): ε₅₂₇ 5660, ε₅₀₀ 5296, ε₃₇₁6455.

FAB-MS (m/z): CHCl₃: 1163.7 ([L₂Cr]⁺).

μ(B.M.)=3.87.

Anal. calcd. for C₄₀H₃₀Br₂CrN₃OSi: C, 59.42; H, 3.74. Found: C, 58.65;H, 3.08.

The molecular structure of the chromium complex is represented in FIG.7.

C. Synthesis of Complex (ONN^(Py))CrBr₂(MeCN)(3b)

Following the same procedure as that used to prepare complex 3a, complex3b was obtained from 0.100 g of 2b (0.192 mmol) and 0.100 g of(p-Tol)CrBr₂(THF)₃ (0.192 mmol) and isolated in an amount of 0.135 g(0.175 mmol) with a yield of 91%.

UV-vis (CH₂Cl₂, 298 K, mol⁻¹·dm³·cm⁻¹): ε₄₉₆ 2865, ε₃₁₉ 7384.

FAB-MS (m/z): CHCl₃: 1090.7 ([ML₂]⁺); acetonitrile: 1090.6 ([L₂Cr]⁺).

Anal. calcd. for C₃₇H₃₀Br₂CrN₃OSi: C, 57.52; H, 3.91. Found: C, 57.11;H, 3.13.

The molecular structure of the chromium complex is represented in FIG.8.

D. Synthesis of Complex (ON-Ph^(F))CrBr₂(MeCN)₂(3c)

Similarly complex 3c was prepared from 0.100 g of 2c (0.168 mmol) and0.087 g of (p-Tol)CrBr₂(THF)₃ (0.168 mmol) and isolated in an amount of0.101 g (0.114 mmol) with a yield of 68%.

UV-vis (CH₂Cl₂, 298 K, mol^(−l)·dm³·cm⁻¹): ε₄₃₈ 6500, ε₃₃₇ 10035, ε₃₀₃9626.

FAB-MS (m/z): C₂H₄Cl₂: 1240.2 ([L₂Cr]⁺).

μ(B.M.)=3.87.

Anal. calcd. for C₃₉H₂₇Br₂CrF₅N₃OSi: C, 52.72; H, 3.06. Found: C, 51.89;H, 2.78.

Homopolymerisation of Ethylene.

The polymerisation was carried out as follows.

A 300 mL glass high-pressure reactor was charged with 80 mL of freshlydistilled toluene under argon flash. Mechanical stirring (Peltonturbine, 1000 rpm) was started, the reactor was then purged withethylene and loaded with a solution of scavenger selected from MAO orDEAC, at atmospheric pressure, and then kept at the desired temperatureby circulating water in a double wall. A solution of pre-catalyst in 2mL of toluene was injected in by syringe. The gas pressure in thereactor was maintained immediately and kept constant with a backregulator throughout the experiment. The ethylene consumption wasmonitored via an Aalborg flowmeter. After a given time period, thereactor was depressurised and the reaction was quenched by adding about5 mL of a 10% solution of HCl in methanol. The polymer was furtherprecipitated by adding 500 mL of methanol, washed and dried in vacuumovernight at room temperature. The polymerisation conditions aresummarised in Table I and the polymerisation results are presented inTable II.

Cat 1 was generated in situ from 2a and (p-Tol)CrBr₂(THF)₃

Cat 2 is generated in situ from 2b and (p-Tol)CrBr₂(THF)₃

Cat 3 is isolated complex 3a

Cat 4 is isolated complex 3b

Cat 5 is isolated complex 3c

The monomer was ethylene.

TABLE I Amount cat Activator/ P_(C2H4) T t Run Cat (μmol) Activator M(bar) (° C.) (min)  1 cat 1 23 MAO 800 1 50 60  2 cat 2 23 MAO 800 1 5060  3 cat1 5 MAO 500 6 50 10 (93)^(a)   4^(b) cat1 21 MAO 800 1 50 60(93)^(a)  5 cat 3 5 DEAC 500 6 50 60  6 cat 3 5 MAO 500 6 50 10 (90)^(a) 7 cat 3 5 MAO 500 1 50 20  8 cat 3 5 MAO 500 6 25 5 (107)^(a)    9^(c)cat 3 5 MAO 500 6 50 10 (94)^(a)  10^(d) cat 3 5 MAO 500 6 50 10(93)^(a) 11 cat 4 5 MAO 500 6 50 10 (83)^(a) 12 cat 5 5 MAO 500 6 50 6013 cat 5 5 DEAC 500 6 50 60 ^(a)The polymerisation reaction proceededexothermally; the maximal temperature reached is given into brackets.^(b)MeCN (4 equiv. vs Cr) was added. ^(c)THF (4 equiv. vs Cr) was added.^(d)Pyridine (4 equiv. vs Cr) was added.

TABLE II Mass Productivity Activity Mn^(e) M_(n) ^(f) Vinyl^(e) T_(m)^(g) Run PE (g) (g_(polym)/g_(cata)) (kgPE/mol/h) (Da) (Da) M_(w)/M_(n)^(f) (mol %) (° C.) 1 3.50 270 151 nd 630 1.99 <40  114 2 0.62 52 271430 800 2.10 67 119 3 9.22 2305 11060 1070 nd nd 85 118 4 1.15 58 551130 nd nd 90 116 5 0.11 27 22 — — — — — 6 11.80 2950 14160 1140 8002.23 90 118 7 4.29 1072 2574 1450 nd nd 90 119 8 9.89 2470 23730 1100 ndnd 87 119 9 8.75 2190 10500 1320 nd nd 88 118 10 12.43 3110 14900 1210nd nd 88 118 11 10.50 2760 12600 1340 850 2.22 91 122 12 0.20 45 40 — —— — — 13 traces — — — — — — — ^(e)Determined from the ¹H NMR spectrum inC₂D₂Cl₄ at 100° C. ^(f)Determined by GPC at 150° C. in trichlorobenzenevs polystyrene standards. ^(g)Determined by DSC.

The invention claimed is:
 1. A pro-ligand of formula I or its tautomeric form of formula I′

wherein R¹, R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from hydrogen, unsubstituted or substituted hydrocarbyl, or inert functional group, wherein two or more of said groups can be linked together to form one or more rings, Z is an atom selected from group 14 of the Periodic Table, each R² is independently selected from a substituted or unsubstituted aryl group having at most 8 carbon atoms, and/or an alkyl group, with the restriction that Z(R²)₃ is a bulky group, at least as bulky as tertio-butyl, R⁸ is CH₂-(2-pyridyl), alpha-quinolone or C₆F₅, possibly containing donor atoms.
 2. The pro-ligand of claim 1, wherein R¹, R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from hydrogen or alkyl group having at most 6 carbon atoms.
 3. The pro-ligand of claim 1, wherein Z is C or Si.
 4. The pro-ligand of claim 1, wherein the donor atoms are halogens or atoms selected from groups 15 and 16 of the periodic Table.
 5. The pro-ligand of claim 1, wherein all R² are the same substituted or unsubstituted phenyl group, higher aromatic group or alkyl having at most 10 carbon atoms.
 6. The pro-ligand of claim 5, wherein R² is unsubstituted phenyl group or tertio-butyl group.
 7. A process for preparing a pro-ligand of formula I or its tautomeric form of formula I′

wherein R¹, R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from hydrogen, unsubstituted or substituted hydrocarbyl, or inert functional group, wherein two or more of said groups can be linked together to form one or more rings, Z is an atom selected from group 14 of the Periodic Table, each R² is independently selected from a substituted or unsubstituted aryl group having at most 8 carbon atoms, and/or an alkyl group, with the restriction that Z(R²)₃ is a bulky group, at least as bulky as tertio-butyl, R⁸ is a unsubstituted or substituted, aliphatic or aromatic hydrocarbyl group, possibly containing donor atoms, the process comprising: providing 2-methoxynaphthalene of formula

reacting the 2-methoxynaphthalene with (R²)₃ZX′, wherein X′ is an halogen, in the presence of sec-BuLi in a solvent to obtain a first compound of formula

reacting the first compound with N-bromosuccinimide to obtain a second compound of formula

reacting the second compound with DMF in the presence of tert-BuLi (two equivalents) in a solvent to obtain a third compound of formula

deprotecting the third compound in order to obtain a fourth compound of formula

condensation of the fourth compound with the appropriate amine R⁸—NH₂ in the presence of catalytic amounts of an acid, to obtain compounds of formula I and its tautomeric form I′


8. The process of claim 7, wherein the acid is HCOOH or p-toluenesulfonic acid (PTSA).
 9. A metallic complex of formula II

wherein M is a metal Group 6 of the periodic Table, each X is the same or different and is an alkyl, benzyl substituted or not, aryl substituted or not, amido, alkoxide, and/or halide and wherein L² is a solvent; and wherein R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from hydrogen, unsubstituted or substituted hydrocarbyl, or inert functional group, wherein two or more of said groups can be linked together to form one or more rings, wherein Z is an atom selected from group 14 of the Periodic Table, wherein each R² is independently selected from a substituted or unsubstituted aryl group having at most 8 carbon atoms, and/or an alkyl group, with the restriction that Z(R²)₃ is a bulky group, at least as bulky as tertio-butyl, and wherein R⁸ is a unsubstituted or substituted, aliphatic or aromatic hydrocarbyl group, possibly containing donor atoms.
 10. The metallic complex of claim 9, wherein either X are all the same and are Br, or one X is para-tolyl and the other X is Br.
 11. A process for preparing the metallic complex of 21 comprising complexing the ligand of claim 1 with metallic salt MX_(n), in a solvent, wherein n is
 2. 12. A catalyst system comprising the metallic complex of claim 9 and an activating agent having an ionising action selected from aluminium alkyl, aluminoxane or boron containing agents.
 13. A process for oligo-, homo- or co-polymerising ethylene and alpha-olefins comprising: injecting the catalyst system of claim 12 into a reactor; injecting ethylene and optional comonomer into the reactor; maintaining the reactor under polymerisation conditions to form oligomers or polymers; and retrieving the oligomers and/or polymer.
 14. The process of claim 13 further comprising introducing comonomer selected from propylene or 1-hexene. 